Experiments will be done to evaluate the possibility that the invasion of arteries by cells of primary cancers is prevented because arterial smooth muscle presents an unfavorable environment. Interactions between cancer cells and arterial and venous smooth muscle will be studied in vitro. Other experiments will explore the effects of dehydration on metastasis. Studies will employ transplantable tumors in mice and rabbits. Additional work will determine if the composition of the surface of tumor cell emboli relates to localization of metastases.